Conventionally, in order to obtain an image with a high contrast, it is preferable that a color filter includes a black mask having a light-intercepting performance so that pixels can be filled by the black mask. The black mask is formed either by using a black organic coloring agent or by using a thin metal film. The latter is more favorable than the former because the former is not superior in light-intercepting performance.
One of the methods for forming the color filter having the black mask composed of a thin metal film is as follows: First, a conductive film such as an ITO which can be etched is formed on a transparent substrate such as a glass, and then, the conductive film is etched to be formed into the configuration of the black mask having a predetermined pattern. Thereafter, the black mask is formed on the conductive film by performing an electroless plating using a metal such as nickel. Thereafter, color patterns are laminated on the black mask.
Another method for forming the color filter is as follows: First, a metal such as chromium is sputtered on a transparent substrate to form it into a thin film thereon, and then, the formed thin film is etched to be formed into the configuration of the black mask having a predetermined pattern. Thereafter, color patterns are laminated on the black mask. According to still another method, a resist is formed on portions, of a transparent substrate, which do not require the formation of the black mask, and then, a metal is sputtered into a thin film on the resist, and then, the resist is removed to form a black mask. Thereafter, color patterns are laminated on the black mask.
In the color filters formed according to these methods, the patterns formed on the thin metal films, or the black masks are formed on the transparent substrates directly or through the conductive films. Therefore, the surface of the thin metal film acts as a specular surface, i.e., images displayed on display devices into which the color filters formed according to these methods are integrated are hard to see depending on visual angles.
In addition to the above-described methods, a method for forming a chromium layer consisting of two layers and having a low reflection has been investigated to improve the method for forming the metal layer by sputtering chromium. But this method is also inappropriate for forming a color filter because a glass plate which is a transparent substrate is warped at a high temperature at which such a chromium layer is formed, and moreover, it costs very much to form a color filter by this method.
It is the object of the present invention to overcome the above-described disadvantages and provide a color filter capable of displaying an image having a high contrast and a method for forming the color filter.